In May 2004, after 11 years and a host of awards, Dr Frasier Crane will be wishing his listeners for the final time, "Goodnight Seattle - and good mental health".

What started life as a spin-off from the comedy Cheers has itself become a phenomenon.

The travails of Dr Frasier and his dysfunctional family and friends have made stars of the regular cast, and enhanced the reputation for comedy of NBC and UK's Channel 4.

When it finishes next year, Frasier will have outstripped the enduring success of its parent sitcom.

Solo trip to Seattle

When Frasier's original creators first got together, their mantra for the series was "no stupid characters and no stupid jokes".

The wit of the Seattle-based sitcom is a triumph for the American system of scripting by committee.

A throng of writers have pitched hundreds of gags for each episode, with only the best surviving until the final draft. The result is a multi-layered script, combining both depth and intelligence.

Kelsey Grammer receives one of his many Emmy awards

David Hyde Pierce, who plays Frasier's brother Niles, describes receiving his lines as "like Christmas morning every week for me".

Frasier Crane alone upped stools from the Boston bar of Cheers, but his writers soon surrounded the neurotic radio psychiatrist with a high-maintenance coterie.

With the effete Niles, their curmudgeonly father Martin, Mancunian housekeeper Daphne, producer Roz and even an obliging Jack Russell, Eddy, Frasier has forged many moments of comic alchemy.

Time to say goodbye

Since its 1993 debut, the show has garnered a record-breaking 30 Emmy awards.

Its title star, Kelsey Grammer, calls Frasier Crane "one of the greatest characters in television history". But, 18 years after first playing him, he feels that the time is right to say goodbye.

We want to stop while it's still great, while people still want to see it

Frasier star Jane Leeves

He only hopes that his alter ego ultimately "gets to find the right girl".

For Grammer, the show's finale will mark the end of an era in an already tumultuous life, marked by family tragedy when his father and sister were both, separately, murdered.

His personal life was marred by marriage woes and a typical Hollywood descent into alcohol and drug abuse

But the actor has no intention of seeking the quiet life. Instead, the ardent Republican plans to embark on a political career, loudly citing his support for George W Bush.

Fading confidence

None of the cast will be hard-up once the series ends. Each episode of Frasier currently boasts a budget of more than $3m, a huge proportion of this covering the wages of Grammer and Pierce.

And playing housekeeper Daphne has made Jane Leeves Britain's best-paid actress, to the tune of £240,000 an episode.

Jane Leeves is Britain's highest-paid actress

Such huge outlays have not stemmed falling ratings, both in the US and abroad.

Although two million British viewers tuned in recently to see Niles finally marry Daphne, many critics felt this oft-postponed union removed much of the comic tension of the previous series.

And, in a sure sign of fading confidence, Channel 4 has moved the show from its long-established Friday slot to one earlier in the week.

Sharp-eyed US comedy acquisitions have long been an essential ingredient of Channel 4's scheduling backbone.

US ratings-winners

Now the end of Frasier coincides with the finale of its fellow ratings-winner, Friends.

Last week, the American cable channel, HBO, also announced that the relative newcomer Sex and the City will probably cease production next year.

Frasier's family, Martin and Niles

The demise of all three at the same time will leave huge gaps in the schedule of a channel that direly needs a ratings-winner.

The popularity of 24, The West Wing and The Sopranos shows that British viewers have lost none of their appetite for a tightly scripted, well-produced US offering.

They're just tiring of Niles and Daphne's post-nuptial cosiness.

With huge syndication fees and commercial revenue, killing the golden goose of a long-running show is a brave act for a television executive.

But when cast members start demanding stratospheric salaries to stay put, and taking control of production, often disastrously, financial returns can start to diminish.

Enduring appeal

When characters have to rely on thinning plots, moving further and further away from the original premise that made them so funny, their credibility is stretched and, with it, viewers' loyalty.

Eddy is often the sanest member of Frasier's household

No cast wants to end up performing ludicrous stunts in place of good storylines, what Americans call "jumping the shark" - a reference to a more-than-surreal late episode of Happy Days which had Fonzie attempting a water ski jump... over sharks.

But, as Frasier approaches its final season, it remains a production of unquestionable style and warmth, with a cast of rare chemistry and a sophisticated script that has withstood the years.

When Dr Crane finally hangs up his headphones and bids his listeners farewell, his show will have become that rare comic treasure that knew when to call it a day.